Optical attenuators are used to optimize the optical power of signals at key points in optical communications networks. For example, in networks having Erbium Doped Fiber Amplifiers (EDFAs), optical attenuators are used between stages of EDFAs to provide constant gain. In Wavelength Division Multiplexed (WDM) systems, optical attenuators are used to adjust optical power of "added" laser signals to match the signal strength of other channels within the network. Optical attenuators can also be used to set signal strength within the range of a particular receiver.
In order to optimize signal strength in fiber optic networks, fiber optic attenuators have been developed. For example, U.S. Pat. No. 5,087,122 issued to Ostrander, et al. (the '122 patent) discloses a blocking beam type attenuator. The '122 patent discloses a vane-line mechanical blocker that is gradually rotated in to a collimated beam to cause light attenuation. The attenuator of the '122 patent provides low insertion loss, low polarization dependent loss, and low wavelength dependent loss.
However, compact size and insensitivity to changes in environmental conditions are desired for most fiber optic components. The attenuator of the '122 patent is not compact in size. Further, the attenuator of the '122 patent is sensitive to mechanical shock and to temperature variations. Thus, the attenuator of the '122 patent requires precise control and special package design, which increases manufacturing costs. What is needed is an improved attenuator for use with fiber optic communications signals.